Ihave 5 math questions and i need asap. only comment if you're gonna me . questions are pasted below.

Which of the following system of equation is not equal to the system of equations is not equal to the system of equations shown below

X+ y = 5 ; x - y =3 solve using linear combination

Solve this riddle: i am an odd number. i an less than 100. the some of my digit is 12. i am a multiple of 15. what number am i?